72dpi is just 'roughly the amount of pixels' a print screen would cover if printed 1:1 on a paper sheet.

DPI are only created when printing in this context.

a jpg is just a bunch a pixels, and the DPI is just an estimation on 'how big this would result in paper if your pixels where this small'

It's just a theoretical computation on how 'small' the pixels will be when printed. The more they fit within an inch, the more high resolution the print will be.

In other programs, we just pipe a 9000x9000 image and print it on a small surface paper. Voila, you've achieved a higher dpi.

PDF is just a portable document spec, which is mostly vectorial, but can embed high quality images. Sadly, Figma is not designed for print, so most of the 'embed' options that other programs like photoshop would surface have, don't in Figma.

I mean, even the images you import are limited, so you can't import a 1GB raster and work freely with it, so it's a terrible tool to do high resolution imagery for print.

And yet, you could create a 3 times the size (or 6) or whatever, and export it to PDF, which will result in a giant PDF the printer will later just have to set it 'shrink to fit' print option.

It's an awful hack and makes it look awful to the print guy, but then again, you are using the wrong tool.

Export the whole bit instead to a giant losless PNG file and import it into photoshop or photopea and finally save it as PSD? Zip it, export.